Methods for monitoring the respiratory function of a person have many applications in medicine, sleep studies, polygraph testing, to name a few. Such systems use wires and electrodes or other physically invasive apparatus which contact the subject and thus may interfere with their convalescence. One important respiratory function desired to be monitored is the concentration of CO2. CO2 deficiency can trigger or exacerbate complaints such as: shortness of breath, chest pain, feelings of suffocation, numbness, irregular heartbeat, to name a few, including fatigue, weakness, exhaustion, nausea, and light-headedness. An assessment of CO2 concentration and respiration rate helps the medical professional better diagnose whether the person is suffering from hyperventilation (overbreathing or hypocapnea) or hypoventilation (underbreathing or hypercapnea). One problem with breathing assessment is that once a patient becomes aware he/she is having their respiration monitored, they tend to unconsciously change their normal breathing pattern. This sometimes makes it difficult to get reliable assessments of a patient's breathing function. An inconspicuous measurement system is highly desirable which can facilitate the assessment of a patient's respiratory function without their participation or even knowledge.
Accordingly, what is needed in this art are increasingly sophisticated methods for assessing a patient's respiratory function in a minimally invasive, non-contact respiration monitoring environment.